This invention relates to mechanism in a valve for blocking and permitting fluid flow through the valve and more particularly, to mechanism for moving a diaphragm between valve open and closed positions.
In U.S. Pat. No. 6,189,861 to Gotch et al, there is disclosed an air actuated diaphragm valve that includes radially spaced inlet and outlet passages opening to one side of a dome shaped diaphragm while a plastic button abuts against the convex center portion of the opposite side of diaphragm. The button is formed from a suitable plastic material having lubricating qualities. The lower surface of the button is slightly convex to match the top concave surface of the valve seat.
Yamaji et al, U.S. Pat. No. 5,295,662, discloses a diaphragm valve having a synthetic resin diaphragm presser (button) abutting against the diaphragm to move it to a valve closed position abutting against a valve seat. The button is mounted by a disc, the valve stem being abuttable against the disc for moving it downwardly while the diaphragm acts to move the button and thereby the disc upwardly. The disc is of a larger diameter than the outer diameter of the valve seat. The valve seat is mounted in a recess defined by radial inner and outer valve body portions that extend to the same elevation.
U.S. Pat. No. 5,820,105 to Yamaji et al discloses a diaphragm presser (button) of a larger diameter than the inner diameter of the valve seat and is made of either synthetic resin (for example, tetrafluoroethylene resin, etc) or synthetic rubber.
Problems encountered with prior art diaphragm valves include diaphragms failing in less cycles of operation than desirable and diaphragms taking an undesirable set.
In order to provide improvements in valves of the above mentioned type and to overcome and/or minimize problems such as mentioned, this invention has been made.